Contrary to popular belief, Finland is not part of Scandinavia. It does, however, fall within the classifications of Nordic and Fennoscandian. Scandinavia specifically refers to Denmark, Norway, and Sweden. This is more historical than geographical: the Kalmar Union brought together the three kingdoms until 1523, and then Norway made its own unions with both Sweden and Denmark. There were actually a few occasions through time when Finland was grouped in with the name, but what really separated it from the other three was a "Pan-Scandinavian" unification movement in the 1830s, which sadly left out Finland. Scandinavia is a Latin term from the first century CE, initially used by Pliny the Elder in his book Natural History. Before that, it came from Proto-Germanic skadinaujo, which meant "Scadia island". We're not exactly sure what Scadia means, but the aujo part comes from PIE akwa, meaning "water".
Adam Aleksic, a rising sophomore studying linguistics and government at Harvard University, has been described as the internet's sixth most famous etymologist. He also has disturbing interests in politics, vexillology, geography, board games, conlanging, and law.